1. Field of the Invention
The invention is directed to an electropneumatic pressure regulating valve having a work chamber and a deaeration chamber separated by a valve seat and a tappet movably guided to and from said valve seat through the work chamber by an electromagnet.
2. Description of the Related Art
A prior art electropneumatic pressure regulating valve is known, for example, from the product catalog "Know-how in Pneumatik" by Mannesmann Rexroth Pneumatik GmbH (11/93, pages 7.026f). This prior art pressure regulating valve controls a pressure corresponding to a predetermined reference value. Integrated regulator electronics compare a reference value to a pressure measured as actual value in a work line by a pressure sensor. The regulator electronics generate a controlling variable therefrom which is supplied to a proportional magnet constructed as an electromagnet, so that this proportional magnet adjusts the predetermined pressure value in the work line by actuating an integrated lift seat-type valve arrangement. The lift valve arrangement is substantially formed of a valve tappet which cooperates with a valve seat and has, for this purpose, a disk face at its end. The valve tappet is guided through a work chamber and is connected at its other end to a magnet armature which is movable longitudinally in the electromagnet.
The pressure regulating valve also has a deaeration connection and a supply pressure connection to perform the task for which it is intended, in addition to a work connection connected with the work chamber. If the pressure in the work line is to be increased corresponding to the controlling variable put out by the regulator electronics, the work connection is connected with the supply connection via the internal seat valve arrangement by the electromagnet until the predetermined higher pressure has been adjusted in the work line. Similarly, if the pressure in the work line is to be decreased, the work connection is connected in a corresponding manner with the deaeration connection until the predetermined lower pressure has been adjusted in the work line.
During the deaeration process mentioned above, an impact pressure dependent on the deaeration lift acts on a lower disk face of the valve tappet corresponding to the valve seat. As a result, the necessary actuation force of the electromagnet acting in the opposite direction increases and reaches its maximum at the greatest deaeration lift. This phenomenon which is known in investigations of the deaeration behavior of valves of this type hinders the capability for precise control of the valve due the change in actuation force by way of the deaeration lift. The unstable states which occur as a result, particularly in a pressure regulating valve, result in a poor ability overall to regulate the pressure in the work line.